Gestational diabetes mellitus (GDM) has emerged as a significant global health challenge, posing risks to maternal, fetal, and neonatal health and contributing to long-term metabolic complications. The increasing prevalence of GDM, driven by rising obesity rates, sedentary lifestyles, and metabolic disorders, underscores the urgent need for effective interventions. While conventional therapies effectively manage maternal glycaemia, they often fall short in addressing associated metabolic risks and may impact fetal development. In this study, we formulated a nanocomposite with phytochemical d-pinitol and hypothesized to study its efficacy in regulating glycemic levels and ameliorating hyperglycemia-induced complications in the GDM rat model. This study involves the development of a nanocomposite incorporating the phytochemical D-pinitol, with the hypothesis that it can efficiently regulate glycemic levels and alleviate complications induced by hyperglycemia in the GDM rat model. The successful synthesis of the NiOSP/dP nanocomposite was validated through multiple analytical techniques. UV-Vis spectroscopy confirmed the synthesis, showing a prominent absorbance peak at 271 nm. Dynamic Light Scattering (DLS) analysis indicated a relatively narrow size distribution, with particle sizes predominantly ranging between 100 and 160 nm. X-ray Diffraction (XRD) analysis revealed several sharp peaks within the 2θ range of 20° to 70°, indicating a well-defined crystalline structure. Fourier-Transform Infrared (FTIR) spectroscopy confirmed the biomolecular composition of the nanocomposite, while Field Emission Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Analysis (FESEM-EDAX) verified its morphology and elemental composition. The NiOSP/dP nanocomposite protected both the fetus from GDM-induced complications and the mother rats, as confirmed by histopathological analysis. It effectively regulated hyperglycemia and hypercholesterolemia in the GDM-induced rats. Additionally, the nanocomposite enhanced antioxidant status and reduced the inflammatory response. Notably, NiOSP/dP treatment significantly downregulated the TLR4/MyD88/NF-κB signaling pathway proteins. Overall, this research demonstrates the therapeutic potential of the NiOSP/dP nanocomposite against GDM-induced rats. It shows potential as an innovative treatment option for addressing GDM in the future.